In semi-automatic or automatic variable-speed transmissions, shifting operations or gearshifts from a currently engaged gear to a target gear are carried out over either one gear step or over several gear steps. The number of gear steps or gears between a currently engaged gear and a target gear in a gearshift operation to be carried out determines the size of the gear step of the gearshift to be carried out.
From DE 10 2005 052 824 A1 it is already basically known that a gearshift from a currently engaged gear to a target gear can be carried out over several gear steps, and this either as a direct shift in a single step or as a combination with a plurality of gearshifts taking place in succession one after another. However, although gearshifts with gear steps of different size are basically known, the specific selection or determination of a gear step, i.e. the determination of the size of a gear step from a currently engaged gear to a target gear remains open in the prior art.
To determine a gear step, namely to determine a gear step from a currently engaged gear to a target gear, the procedure adopted in practice is that by virtue of a performance characteristic the size of the gear step is determined as a function of a driving resistance of the motor vehicle. For this, the driving resistance can be determined by computation or by measurement. In practice, when a suitable gear step has been determined for a currently engaged gear and a current driving resistance on the basis of a performance characteristic, the corresponding gearshift operation is carried out when a so-termed shifting rotational speed has been reached.
This procedure known from prior practice for determining the size of a gear step, which is carried out as a function of the currently engaged gear and as a function of the current driving resistance with reference to the performance characteristic, has the disadvantage that different performance characteristics have to be prepared and stored for different drive aggregates. Thus, a performance characteristic for one drive aggregate cannot simply be used with another drive aggregate of different power. This fact increases the cost and effort of matching up in the case of transmissions that can be used with a variety of drive aggregates.